In UCE EFI bikes, different kinds of spark plugs have been used, tested, discussed but I had not seen a real comparison of how deep they are inside the cylinder - which will determine the location of spark above the piston. If it is too close to piston, it will act as timing is too advanced and too far away from piston it will feel like the timing is retarded. That can affect the engine performance and likelyhood of piston damage.

UCE EFI bikes are originally fitted with Bosch WD7 DDC4 spark plug with Dual Electrodes which are on either side of the central electrode. Took this picture to compare the lengths of NGK Non-Projected (B8ES) and Projected (BPR 6ES) spark plugs with the Bosch plug.

It explains many of the common aspects of spark plugs including projection:"A projected spark plug protrudes into the combustion chamber further and provides higher ignitability and improved performance. Simply this can be understood by representing the combustion chamber as a circle. A projected spark plug in effect produces a spark in the middle of the circle (or combustion chamber) allowing for an even flame spread. Conversely, a non-projected spark plug means the flame spread is not even."

It also explains the precious metal electrode nicely. Since it has a higher melting point it can be narrower and again, gives you a cleaner, more precise spark resulting in better performance, whiter whites, britghter colors, and world peace I think at least one user noted better performance (notably more stable idle IIRC) with a precious metal plug.Scott

It also explains the precious metal electrode nicely. Since it has a higher melting point it can be narrower and again, gives you a cleaner, more precise spark resulting in better performance, whiter whites, britghter colors, and world peace I think at least one user noted better performance (notably more stable idle IIRC) with a precious metal plug.Scott

Hey Folks, I run Bosch dual electrode plugs in my Enfield and my 79" Harley Shovelhead. I also run dual electrode plugs in my Cessna 150. As far as I know, all air cooled aircraft engines run dual electrode plugs for reliability. That's good enough reason for me to use them in my motorcycles. Just my opinion !

300-600 miles Iridium NGK BR8EIX - synthetic oil, great starting and idle, and electrode came out as expected with a thin layer of fluffy carbon.

600-800+ miles Iridium NGK BPR6EIX - another synthetic oil change, great idle and running, starting is a bit flaky but no stalls........I can almost feel slightly better acceleration (or maybe the engine is simply more broken in)

Hey Folks, I run Bosch dual electrode plugs in my Enfield and my 79" Harley Shovelhead. I also run dual electrode plugs in my Cessna 150. As far as I know, all air cooled aircraft engines run dual electrode plugs for reliability. That's good enough reason for me to use them in my motorcycles. Just my opinion !

And a GOOD opinion it is! The REASON that these particular plugs were chosen is the fact that the flame kernel is not occluded by the ground electrode - the same reason they are used in aircraft engines, where a single misfire could have dramatic consequences. Using a projected tip plug WILL get the flame kernel started down in the "sweet spot" of the reactible gas in the chamber (Henry Yunick patented them for just that reason ...) I have found that if the heat range is correct for the mixture that you are running, the single electrode plugs are just fine. The ONLY difference that i found was in the hot starting - it usually took a couple more cranks (literally two ...) to fire the lean-ass mixture in the hole with the single electrode plug .... but that's ALL.

Jjoe 226 has it right with his ..... they are PERFECT as for what they should be .... Of course the ULTIMATE plug would be a surface gap one .....

. The ONLY difference that i found was in the hot starting - it usually took a couple more cranks (literally two ...) to fire the lean-ass mixture in the hole with the single electrode plug .... but that's ALL.

Jjoe 226 has it right with his ..... they are PERFECT as for what they should be .... Of course the ULTIMATE plug would be a surface gap one .....

I figured out my hot starting. Using the kick start, which I normally do, I ease past 1 TDC and the bike fires first kick. Cold start, with "choke", 2 eases and first kick fires. Every time. NGK BR6ES